It is known in the prior art to use retainer blocks having a cylindrical central aperture wherein a ball lock is positioned therein and is spring loaded to lock in place a punch shank. Punches that are insertable therein are also known to have an elongated shank having a teardrop cutaway for locking with the spring loaded ball lock of the retainer block. Punches and retainers of this type are well known and described in detail in several catalogs and publications such as "Catalog 1000" by Pivot Punch Corporation of Lockport, N.Y. which is hereby incorporated by reference herein. This catalog describes the state of the art pucnhes, ball locks, die buttons, ball lock retainers and other standard products.
U.S. Pat. No. 1,860,998 also describes a tool holder wherein a ball lock retainer and teardrop containing type punches are used. This patent desscribes the ball-locking mechanism used to retain tools or punches in position. The provision of a tool holder is described having this locking element mounted in the retainer and so arranged that a maximum bearing is imparted on the periphery of the tool.
In all these prior art systems and arrangements there is used a stripper plate which removes the metal being worked on from the punch. The central hole of the stripper plate is always wider than the circumference of the punch. The punch extends from and through the stripper plate upward and into the retainer block. When the punch needs to be changed because it becomes worn, broken, dull or needs to be changed for a changeover of tooling or punch needs, it is always required in the prior art to first remove the stripper plate. Thus, in order to have access to the punch for removal, it is necessary to remove first the stripper plate. Generally, one would use a ball depressor to first push the ball lock out of contact with the punchshank and pliers are used to remove the punch. After the punch is sharpened or replaced, it is then reinserted or inserted into the retainer aperture to again depress the ball lock and lock the punch into position. The punch is then rotated to make sure it is locked in place when the ball depressor is removed. After this is compelted, the stripper plate is then reattached to the die. This complete process is very time consuming and when several units are involved, the changeover time becomes significant.
Each prior art retainer block is equipped with a small guide aperture (adjacent the central punch receiving hole) which is adapted to receive a ball depressor to loosen the grip or unlock the punch shank. After the stripper plate has been removed, the ball depressor is inserted into this guide aperture and the punch shank removed from the retainer hole. This ball depressor cannot be inserted without first removing the stripper plate since the stripper plate blocks access thereto. Therefore, to remove present punches one would require an allen wrench to fit stripper bolts, a pliers or vice grip to grab the punch with to remove it from the retainer block.